Color filter and method of producing the same

ABSTRACT

The color filter of the present invention is particularly suitable for a color liquid crystal display (1). Colored pixels (8, 9 and 10) each made of a transparent resin material having a pigment dispersed therein are formed on a transparent substrate (6). The color filter has a protective film (11) formed over the colored pixels by curing a coating film of a photopolymerizable resin composition containing at least a photopolymerizable acrylate oligomer and a multifunctional photopolymerizable acrylate monomer having at least two functional groups in one molecule. The color filter is superior in both heat resistance and light resistance and also excellent in display quality.

TECHNICAL FIELD

The present invention relates to a color filter having a colored layersuperior in both heat resistance and light resistance and a protectivelayer that has excellent evenness and high strength. More particularly,the present invention relates to a color filter used in a color liquidcrystal display and a method of producing the same.

BACKGROUND ART

A liquid crystal display comprises two transparent substrates, forexample, glass substrates, provided with transparent electrodes anddisposed with a gap of the order of 1 μm to 10 μm provided therebetween,and a liquid crystal material sealed in the gap, wherein the liquidcrystal is orientated in a predetermined direction by application of avoltage between the electrodes, thereby forming transparent and opaqueportions, and thus displaying an image. In a color liquid crystaldisplay, a color filter for three colors, i.e., red (R), green (G) andblue (B), corresponding to the three primary colors of light areprovided over either of the transparent electrode substrates to effectadditive color mixture of the three primary colors by the shutter actionof the liquid crystal, thereby displaying a desired color.

Such a color filter for a color liquid crystal display comprises atransparent substrate, a colored layer, a protective film, and atransparent electrically conductive film, which are stacked in thementioned order. The color filter is disposed to face anothertransparent substrate, which has electrodes or thin-film transistorsformed in opposing relation to the colored pixels of the three primarycolors, i.e., R, G and B, with a gap of several μm held therebetween,and a liquid crystal substance is sealed in the gap, thereby forming aliquid crystal display.

FIG. 1 is a sectional view of one example of the color liquid crystaldisplay. The color liquid crystal display 1 includes a color filter 2and an opposing substrate 3 formed with thin-film transistors (TFT) ortransparent electrodes. The color filter 2 and the substrate 3 aredisposed to face each other across a predetermined gap and bondedtogether by using a sealing medium 4 formed by mixing reinforcing fiberswith an epoxy resin material or the like. A liquid crystal 5 is sealedin the space defined between the color filter 2 and the TFT substrate 3.

The color filter 2 will be explained below more specifically. Asubstrate 6, for example, a glass substrate, has a black matrix 7 formedthereon so as to divide adjacent colored pixels by using a metal, e.g.,chromium, or a resin material colored with a dye or a pigment, thusforming a colored layer comprising colored pixels of the three primarycolors, that is, red colored pixels 8, green colored pixels 9, and bluecolored pixels 10, which are divided from each other by the black matrix7. In addition, a protective film 11 is provided over the colored layerto protect it, and a transparent electrode film 12 for driving theliquid crystal is provided over the protective film 11. Further, anorientation layer 13 for orientating the liquid crystal is formed overthe transparent electrode film 12.

Hitherto, colored pixels provided on the color filter are formed asfollows. A transparent substrate, for example, a glass substrate, iscoated with a transparent resin material obtained by adding aphotosensitive material, e.g., a dichromate, a chromate, or adiazocompound, to a hydrophilic resin material, e.g., polyvinyl alcohol,polyvinyl pyrrolidone, gelatin, casein, or glue, thereby forming atransparent photosensitive resin layer. Then, a photomask having anopening pattern with a predetermined configuration is placed over thetransparent resin layer, and exposure and development are carried out toform a first resin layer, which is then dyed with a desired dye to formfirst transparent colored pixels. Next, a transparent hydrophobic resinfilm for preventing dyeing is formed over the first transparent coloredpixels in order to prevent migration of the dye. Thereafter, secondtransparent colored pixels are formed in the same way as in the case ofthe first transparent colored pixels. By repeating the above-describedprocess, transparent colored pixels of at least two or three differentcolors are formed on the substrate.

However, the above-described method requires formation of a transparentresin film for preventing dyeing for each color in order to providetransparent colored pixels of a plurality of colors and hence suffersfrom the disadvantage that the production process is extremelycomplicated.

In addition, the color filter for a color liquid crystal display has atransparent electrode film formed thereon for driving the liquidcrystal. The transparent electrode film is formed mainly by using an ITOfilm that is a composite oxide comprising indium oxide and tin oxide,which has excellent characteristics. However, since the electricalresistance of the ITO film depends on the film forming temperature, itis necessary in order to obtain an ITO film of low resistance to carryout the film forming process by heating at a temperature of about 300°C. However, the conventional color film having transparent pixelscolored by using a dye has a probability that the dye-colored layer willbe caused to change color by heat applied during a manufacturingprocess, e.g., the ITO film formation, or light externally appliedduring use. Thus, the prior art is limited in the heat resistance andthe light resistance, so that the conventional color liquid crystaldisplay equipped with such a color filter is not satisfactory.

It may be considered using a thermosetting resin material which enduresthe heat treatment in the manufacturing process as a protective film forthe color filter. However, in the case of a thermosetting resinmaterial, the protective film is formed over the whole surface of thecolor filter and it is difficult to limit the area where the protectivefilm is formed to a predetermined region.

If the protective film is formed over the whole surface of the colorfilter, the color filter and the opposing substrate are bonded by asealing medium with the protective film interposed therebetween, so thatno adequate bond strength can be obtained. In a case where the colorfilter is judged to be defective in display quality on inspection afterthe color filter and the opposing substrate have been bonded togetherand the sealing medium and the tab are successively separated in orderto reuse the color filter, if the colored layer has a protective layeron the outer peripheral portion thereof, the transparent electrode filmformed on the color filter is undesirably separated together with thesealing medium or the tab, resulting in a failure to reuse the colorfilter.

Under these circumstances, it has also been a conventional practice toemploy a photo-setting resin material which enables a region where it isset to be readily limited by using a photomask, in order to limit thearea where the protective film is formed to a specific region. However,a photosensitive polyimide resin material which has heretofore been usedas a photo-setting resin material is highly hygroscopic, inferior in theresistance to corrosion from an alkaline solution used in the formationof electrodes or other process and costly and hence undesirable forpractical use. In addition, a photosensitive acrylic resin materialwhich has also heretofore been used is inferior in the resistance toheat and also involves the problem that cracks or wrinkles may grow onthe color filter when a relatively thick transparent electricallyconductive film is formed on the protective film with a view to loweringthe electrical resistance.

If the surface of the protective film is not even, the transparentelectrode film becomes uneven, so that the gap between the color filterand the opposing substrate varies locally, resulting in differences inthe optical rotatory power of the liquid crystal. Thus, unevenness ofdisplay results.

Further, if a photo-setting resin material is set by irradiation withlight, e.g., ultraviolet light, by using a photomask, it is possible tolimit the area where the protective film is formed. In such a case,however, since the protective film is formed in a pattern faithful tothe pattern of the photomask, a step corresponding to the thickness ofthe protective film is produced at the peripheral edge portion of theprotective film set. If a transparent electrode film for driving theliquid crystal is formed over such a protective film, it extends as faras the peripheral portion of the substrate beyond the area where theprotective film is formed, so that the transparent electrode film is notso thick at the step portion as it is at the even portion. Thus, aproblem in terms of strength arises. In particular, when the transparentelectrode film is etched in patterns corresponding to a large number ofpixels, side etching progresses particularly at the step portion, sothat there is a possibility of disconnection of the transparentelectrode film.

It is an object of the present invention to provide a color filterhaving a colored layer comprising colored pixels, which is excellent inboth heat resistance and light resistance, and a protective film whichis superior in heat resistance, satisfactorily hard and excellent inadhesion to the substrate and which has a gentle step at the peripheralportion of the substrate, and also provide a method of producing thecolor filter.

DISCLOSURE OF THE INVENTION

The color filter according to the present invention is characterized bycomprising transparent colored pixels in which the light transmittancein the light absorbing region on the spectral characteristic curve inthe visible region is not more than 20%, while the light transmittancein the light transmitting region is not less than 50%, the transparentcolored pixels being provided on a substrate in patterns of a pluralityof colors by using a transparent resin material having a pigmentdispersed therein which has spectral characteristics to transmit lightin a specific region in the visible region, the pigment further havingsuch a particle diameter distribution that particles having a particlediameter of 1 μm or more comprise not more than 10% of all the pigmentparticles by weight and particles having a particle diameter in therange of from 0.01 μm to 0.3 μm comprise not less than 60% of all thepigment particles by weight. The pigment dispersed in the transparentresin material preferably has such a particle diameter distribution thatparticles having a particle diameter of 1 μm or more comprise not morethan 5% of all the pigment particles by weight.

The color filter of the present invention is further characterized byemploying as a protective film formed over the colored layer aphotosensitive acrylic resin material obtained by adding amultifunctional photopolymerizable acrylate monomer having a pluralityof functional groups in one molecule to a photopolymerizable acrylateoligomer. The color filter of the present invention is furthercharacterized by employing a photosensitive resin material obtained byadding a multifunctional photopolymerizable acrylate oligomer to amixture of a photopolymerizable acrylate oligomer and an epoxy resin. Inaddition, the color filter of the present invention is characterized byemploying a photosensitive resin material obtained by adding amultifunctional photopolymerizable acrylate oligomer to aphotopolymerizable acrylate oligomer comprising an epoxy acrylate inwhich a part of the acrylate groups are epoxy groups.

In addition, the color filter of the present invention is characterizedin that the protective film is formed by exposing the above-describedresin composition coated on the colored layer through a photomask insuch a manner that the distance between the photomask and the substrateis greater than the distance therebetween that is proper for exposure,thereby reducing the quantity of light at the peripheral portion of theexposed region so that the step of the protective film becomes gentle.

In addition, the color filter of the present invention is characterizedin that a silane coupling agent is coated on a transparent substratebefore the formation of the protective film, or a silane coupling agentis mixed with the above-described resin composition, thereby increasingthe strength of the transparent substrate and the protective film at theperipheral portion of the latter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a sectional view of a color liquid crystal display. FIGS.2a-2d shows a process for producing a color filter. FIGS. 3a-3c shows aprocess for forming a protective film over a colored layer. FIGS. 4a-4cis a sectional view showing unevenness of a protective film. FIGS. 5a-5bis a sectional view showing the change in the thickness of theperipheral edge portion of a protective film. FIG. 6 schematically showsexposure by a proximity aligner. FIG. 7 shows the conditions of exposurein a case where the distance between a photomask and a substrate isgreater than the correct one. FIG. 8 is a graph showing the relationshipbetween the distance for exposure by a proximity aligner and themagnitude of the angle of inclination of the peripheral edge portion ofthe resulting protective film.

BEST MODE FOR CARRYING OUT THE INVENTION

The color filter according to the present invention is characterized bycomprising transparent colored pixels in which the light transmittancein the light absorbing region on the spectral characteristic curve inthe visible region is not more than 20%, while the light transmittancein the light transmitting region is not less than 50%, the transparentcolored pixels being provided on a substrate in patterns of a pluralityof colors by using a transparent resin material having a pigmentdispersed therein which has spectral characteristics to transmit lightin a specific region in the visible region, the pigment further havingsuch a particle diameter distribution that particles having a particlediameter of 1 μm or more comprise not more than 10% of all the pigmentparticles by weight and particles having a particle diameter in therange of from 0.01 μm to 0.3 μm comprise not less than 60% of all thepigment particles by weight. The pigment dispersed in the transparentresin material preferably has such a particle diameter distribution thatthe particles having a particle diameter of 1 μ m or more comprise notmore than 5% of all the pigment particles by weight.

The color filter of the present invention is further characterized byemploying as a protective film formed over the colored layer aphotosensitive acrylic resin material obtained by adding amultifunctional photopolymerizable acrylate monomer having a pluralityof functional groups in one molecule to a photopolymerizable acrylateoligomer. The color filter of the present invention is furthercharacterized by employing a photosensitive resin material obtained byadding a multifunctional photopolymerizable acrylate oligomer to amixture of a photopolymerizable acrylate oligomer and an epoxy resin. Inaddition, the color filter of the present invention is characterized byemploying a photosensitive resin material obtained by adding amultifunctional photopolymerizable acrylate oligomer to aphotopolymerizable acrylate oligomer comprising an epoxy acrylate inwhich a part of the acrylate groups are epoxy groups. In addition, thecolor filter of the present invention is characterized in that theprotective film is formed by exposing the above-described resincomposition coated on the colored layer through a photomask in such amanner that the distance between the photomask and the substrate isgreater than the distance therebetween that is proper for exposure,thereby reducing the quantity of light at the peripheral portion of theexposed region so that the step of the protective film becomes gentle.

With the above-described arrangement, it is possible to obtain a coloredlayer which is excellent in display quality and superior in both heatresistance and light resistance and a protective film which is increasedin the degree of crosslinking so as to be rigid and hard, so that nocrack or wrinkle will grow even if a thick transparent electrode film isformed over the protective film. Even when recesses are formed betweenadjacent colored pixels or the upper sides of colored pixels are uneven,irregularities in the surface of the protective film at positionscorresponding to the uneven portions are extremely small, so that it ispossible to obtain a protective film which has extremely smallirregularities in the surface and which is therefore excellent inevenness.

Pigments which are generally employed for colored pixels have a particlediameter which is considerably larger than that of the pigment employedin the present invention and are therefore unsatisfactory in terms oftransparency. For this reason, the conventional pigments are not usedfor purposes in which transmitted light is utilized. Even if such aconventional pigment is used for a color filter or the like, no productthat has an adequate sensitivity can be obtained because of the lowtransmittance. If such a color filter is used for a color liquid crystaldisplay, the brightness of the image obtained is not satisfactory. Inaddition, the scattering of light by the pigment particles is large, sothat the polarization is disordered. Accordingly, in a liquid crystaldisplay that effects display by utilization of polarization, imagedisplay characteristics such as contrast ratio deteriorate.

Further, the present invention makes use of the characteristics that thelowering of the light transmittance due to the scattering of light isreduced and the transparency of the resulting colored pixels increasesto a level adequate for practical use by setting the particle diameterof a pigment dispersed in a transparent resin material so as to be notlarger than the wavelength of incident light and also setting theparticle diameter distribution of the pigment within a specific range.

Examples of the above-described transparent resin material usable in thepresent invention are photosensitive resin materials having aphotosensitive group, and transparent resin materials endowed withphotosensitivity by a photo-crosslinking agent. In particular, water-,oil- or alcohol-soluble photosensitive resin materials are preferable.More specifically, compounds mentioned below are usable.

(A) Water-soluble photosensitive resins having a photosentive group:

Polyvinyl alcohol derivative resins, e.g., polyvinyl alcohol resin, andpolyvinyl alcohol/stilbazolium resin.

(B) Oil-soluble photosensitive resins having a photosensiive group:

Photo-crosslinkable photosensitive resins, e.g., cinnamic acid compound,photodecomposition crosslinking photosensitive resins, e.g., bisazidecompound, photodecomposition polarity change type photosensitive resins,e.g., o-quinonediazide compound, etc.

(C) Combinations of binder resins (1) and photo-crosslinking agents (2)such as those mentioned below.

(1) Binder resins:

(i) animal proteins, e.g., gelatin, casein, and glue;

(ii) celluloses, e.g., carboxymethylhydroxyethyl cellulose, hydroxyethylcellulose, hydroxypropyl cellulose, and methyl cellulose;

(iii) vinyl polymers, e.g., polyvinyl alcohol, polyvinyl pyrrolidone,polyvinyl methyl ether, polyacrylic acid, polyacrylamide, polydimethylacrylamide, and copolymers of these polymers;

(iv) ring-opening polymers, e.g., polyethylene glycol, and polyethyleneimine;

(v) condensates, e.g., water-soluble nylon; and

(vi) oil-soluble resins, e.g., butyral resin, styrenemaleic acidcopolymer, chlorinated polyethylene or chlorinated polypropylene,polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinylacetate, acrylic resin, polyamide, polyester, phenol resin, andpolyurethane resin.

(2) Photo-crosslinking agents:

Dichromates, chromates, diazocompounds, bisazide compounds, etc.

(D) Combinations of the above-mentioned binder resins (1) and thefollowing monomers or oligomers (2) and initiators (3).

(2) Monomers or oligomers:

Acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxypropylacrylate, 2-hydroxypropyl methacrylate, vinyl acetate, N-vinylpyrrolidone, acrylamide, methacrylamide, N-hydroxymethyl acrylamide,N-(1,1-dimethyl-3-oxobutyl) acrylamide, polyethylene glycol diacrylate,polyethylene glycol dimethacrylate, methylene bisacrylamide,1,3,5-triacryloyl-1,3,5-triazocyclohexane, pentaerythritol triacrylate,styrene, vinyl acetate, various kinds of acrylic ester, various kinds ofmethacrylic ester, acrylonitrile, etc.

(3) Initiators:

(i) photodecomposition type initiators, e.g., azobisisobutyronitrile,benzoin alkyl ether, thioacridone, benzil, N-(alkylsulfonyloxy)-1,8-naphthalene dicarboxyimide, 2,4,6-tri(trichloromethyl)triazine, etc;

(ii) hydrogen transfer type initiators, e.g., benzophenone,anthraquinone, 9-phenylacridine, etc.

(iii) electron transfer type composite initiators, e.g.,benzanthrone/triethanolamine, Methylene Blue/benzene sulfinate,triarylimidazolyl dimer/Michler's ketone, carbon tetrachloride/manganesecarbonyl, etc.

In the present invention, a pigment is dispersed in a transparent resinmaterial such as those described above to obtain a transparent resincomposition for forming transparent colored pixels.

In this specification, the term "pigment" is employed to mean coloringpowders which are only slightly soluble in water or an organic solvent,including organic and inorganic pigments. It should be noted that acertain kind of dye is only slightly soluble in water or an organicsolvent and this kind of dye may be employed as "pigment" in the presentinvention.

Examples of organic pigments usable in the present invention includeazo-lake pigments, insoluble azo-pigments, condensation azo-pigments,phthalocyanine pigments, quinacridone pigments, dioxazine pigments,isoindolenone pigments, anthraquinone pigments, perinone pigments,thioindigo pigments, perylene pigments, and mixtures of these pigments.

Examples of inorganic pigments usable in the present invention includeMilori blue, cobalt violet, manganese violet, ultramarine blue, Prussianblue, cobalt blue, cerulean blue, viridian, emerald green, cobalt green,and mixtures of these pigments.

It is preferable that the pigment dispersed in the transparent resinmaterial have such a particle diameter distribution that particleshaving a particle diameter of 1 μm or more comprise not more than 10%,preferably not more than 5%, more preferably not more than 2% of all thepigment particles by weight. If pigment particles having a particlediameter of 1 μm or more are dispersed in the photosensitive resinmaterial in excess of 10% of all the pigment particles, the lighttransmittance lowers undesirably due to the scattering of light and thelike. On the other hand, the pigment that is employed in the presentinvention needs to have such a particle diameter distribution thatparticles having a particle diameter in the range of from 0.01 μm to 0.3μm comprise not less than 60% of all the pigment particles by weight. Bysatisfying both the above-described conditions for the particle diameterdistribution, it is possible to suppress effectively the lowering in thelight transmittance due to the scattering of light and hence possible toobtain excellent spectral characteristics suitable for the color filter.

A pigment having such a particle diameter distribution and a transparentphotosensitive resin material are mixed together in a solid contentratio of 1/10 to 2/1, preferably 1/5 to 1/2, thereby obtaining aphotosensitive resin composition for forming transparent colored pixels.A proper combination of a pigment and a transparent resin material isselected by taking into consideration the spectral characteristics ofthe pigment and those of the transparent resin material.

To form transparent colored pixels having a pigment dispersed thereinwhich has a desired particle diameter distribution such as thatdescribed above, first, the pigment that has been considerably finelypowdered and a solution of a transparent resin selected from thosedescribed above are mixed together, and the resulting mixture is groundin a pigment dispersing mill, e.g., a triple roll mill, a ball mill, ora sand mill. After the pigment has been thoroughly dispersed, thedispersion is centrifuged or filtered by using a glass filter, amembrane filter or the like to remove relatively large pigment particleshaving a particle diameter of 1 μm or more, thereby obtaining apigment-containing transparent resin composition. Alternatively, thepigment is mixed with a solution of a binder resin which is compatiblewith the transparent resin, and after the pigment has been thoroughlydispersed in the same way as the above, the dispersion is centrifuged orfiltered by using a glass filter, a membrane filter or the like toremove relatively large pigment particles having a particle diameter of1 μm or more, thereby forming a coloring agent, which is then mixed withthe above-described transparent resin, thus forming a pigment-containingtransparent resin composition.

It is preferable to add a nonionic surface active agent as a dispersantfor improving the dispersibility of the pigment when it is dispersedinto the transparent resin. It is also preferable that the viscosity ofthe transparent resin composition or the coloring agent, in which thepigment is dispersed, should be adjusted to 500 cps (temperature: 25°C.) or less when pigment particles having a relatively large particlediameter are removed from the composition or the coloring agent.

Next, one example of the method of producing transparent colored pixelsconstituting a color filter by employing a transparent resin compositionprepared as described above will be explained with reference to thedrawings.

As shown in FIG. 2(A), after a black matrix 22 is formed on atransparent substrate 21, a pigment-containing photosensitive resincomposition prepared as described above is coated over the substrate 22by a coater, e.g., a spin coater, a roll coater, a dip coater, a wheelcoater, or a bar coater, so that the thickness of the dry film is on theorder of 0.1 μm to 10 μm, preferably 0.5 μm to 3 μm, thereby forming aresin coating layer 23 for colored pixels. After being dried, thecoating layer 23 is irradiated with ionizing radiations 25, e.g.,ultraviolet rays, by using a light source, e.g., a xenon lamp, a metalhalide lamp, or an extra-high pressure mercury lamp, through a photomask24 having predetermined opening patterns, thereby effecting patternexposure, as shown in FIG. 2(B). As a result of the pattern exposure,exposed portions 26 corresponding to the pattern are formed on thecoating layer 23. In the case of a negative photosensitive resin,insolubilized portions are formed, whereas, in the case of a positivephotosensitive resin, solubilized portions are formed. Then, thesolubilized portions are selectively removed by spray development or dipdevelopment with water or a developing solution comprising, for example,water and an organic solvent, as shown in FIG. 2(C). Upon completion ofthe above-described process, first colored pixels 27 are formed. Thus,by repeating a similar process a plurality of times, transparent coloredpixels of a plurality of colors can be provided on the substrate withoutforming a transparent resin film for preventing dyeing, as shown in FIG.2(D).

For example, as stated in Examples described later, first, a coatingfilm of a transparent photosensitive resin composition (the lighttransmittance in the light absorbing region after the formation of thecoating film of this photosensitive resin is not more than 20%, and thelight transmittance in the light transmitting region is not less than50%), in which is dispersed a pigment of a first hue selected from amongred, green and blue, is formed on a transparent substrate according tothe above-described process. Then, the coating film of thephotosensitive resin composition is exposed through photomask patterns,and the coating film exposed in this way is developed to thereby formfirst patterned transparent colored pixels on the transparent substrate.Then, for a second hue and, if necessary, for a third hue, a processsimilar to that for the first patterned transparent colored pixels,described above, is repeated to form second and third patternedtransparent colored pixels, thereby obtaining a color filter.

In this case, the transparency of the colored pixels of the color filterobtained as an end product is determined by the kind of transparentresin employed as a base, the kind and amount of pigment dispersed inthe transparent resin, the thickness of the colored pixel layer providedon the substrate, etc. First, it is preferable that a transparent resinthat is employed as a base have a light transmittance of not lower than80%, preferably not lower than 90%, more preferably not lower than 95%,in the entire range of from 400 nm to 700 nm, which is the visibleregion. A pigment is dispersed into the transparent resin that forms abase, and the resulting dispersion is coated on a substrate to apredetermined film thickness. After the formation of the coating film,the light transmittance in the absorbing region is preferably not morethan 20%, more preferably not more than 10%, and at the same time, thelight transmittance in the transmitting region is preferably not lessthan 50%, more preferably not less than 60%, although the absorbing andtransmitting regions change in accordance with the kind of pigmentemployed.

It is assumed that when the above-described conditions are satisfied,the colored pixels of the color filter can be regarded as "transparent".

It should be noted that a transparent glass, a transparent resin film,etc. may be employed as a transparent substrate.

Next, a protective film of a photopolymerizable resin composition whichis formed over the colored layer will be explained in detail.

Photopolymerizable acrylate oligomers having a molecular weight of theorder of 1,000 to 2,000 are preferably used for the protective film ofthe color filter according to the present invention. Examples of sucholigomers are polyester acrylates, epoxy acrylates, e.g., phenolicnovolak epoxy acrylate, and o-cresol novolak epoxy acrylate,polyurethane acrylates, polyether acrylates, oligomer acrylates, alkydacrylates, polyol acrylates, melamine acrylates, and oligomers in whicha part of the acrylate groups are epoxy groups.

Examples of epoxy resins which can be mixed with a photopolymerizableresin composition are phenol novolak type epoxy resins represented bythe structural formula 1 and cresol novolak type epoxy resinsrepresented by the structural formula 2. ##STR1##

In the case of employing an acrylate oligomer comprising an epoxyacrylate in which a part of the acrylate groups are epoxy groups, theproportion of epoxy groups in the oligomer is preferably set 10 parts to40 parts by weight of epoxy groups, to satisfy the conditions where theresin is set on irradiation with ultraviolet rays.

An epoxy acrylate can be produced by a reaction of a glycidyl ether withacrylic acid in such a manner that the epoxy groups of the precursor areallowed to remain. One example of such oligomers is shown below.##STR2##

Examples of multifunctional photopolymerizable acrylate monomers are1,4-butanediol diacrylate, diethylene glycol diacrylate, neopentylglycol diacrylate, pentaerythritol triacrylate, trimethylolpropanetriacrylate, pentaerythritol acrylate, dipentaerythritol hexaacrylate,etc.

In addition, if a photopolymerizable acrylate monomer or oligomer isgiven an alkali-reactive group, e.g., a carboxyl group, it becomescapable of being developed with an alkaline aqueous solution, so thatthe handling of the developing solution and the disposal of the wasteliquor are facilitated in comparison with the development using anorganic solvent. Thus, the use of such a photopolymerizable acrylatemonomer or oligomer is preferable from the viewpoint of economy andsafety.

It is also possible to add an initiator, e.g., benzophenone, Irgacure184, Irgacure 907, Irgacure 651 (trademarks; manufactured by Ciba-GeigyLtd.), or Darocure (trademark; manufactured by Merck & Co., Inc.), tothe photopolymerizable resin material in a solid content ratio of about1 to 3%.

In addition, a photocationic catalyst such as an aryl diazonium salt isadded as an epoxy curing agent. Epoxy curing agents comprising aminesare not preferable because these agents cause the resin to yellow.

If a silane coupling agent is coated on a transparent substrate beforethe coating of the resin composition or it is added to the resincomposition, the bond strength can be increased. In this case, a largevariety of commercially available silane coupling agents can be used,but it is particularly preferable to use γ-(2-aminoethyl)-aminopropyltrimethoxy silane, γ-aminopropyl triethoxy silane,γ-glycidoxypropyltrimethoxy silane, etc.

The following are particularly preferable examples of the composition ofa photopolymerizable acrylate oligomer, an epoxy resin and amultifunctional photopolymerizable monomer.

    ______________________________________                                        Composition Example 1:                                                        Phenol novolak epoxy acrylate                                                                           . . . 60%                                           Trimethylolpropane triacrylate                                                                          . . . 17%                                           Dipentaerythritol hexaacrylate                                                                          . . . 20%                                           Irgacure 184              . . . 3%                                            Composition Example 2:                                                        o-cresol novolak epoxy acrylate                                                                         . . . 60%                                           Dipentaerythritol hexaacrylate                                                                          . . . 38%                                           Irgacure 184              . . . 2%                                            Composition Example 3:                                                        Polyurethane acrylate     . . . 50%                                           Dipentaerythritol hexaacrylate                                                                          . . . 48%                                           Irgacure 651              . . . 2%                                            Composition Example 4:                                                        Melamine acrylate         . . . 70%                                           Trimethylolpropane triacrylate                                                                          . . . 27%                                           Irgacure 184              . . . 3%                                            Composition Example 5:                                                        Phenol novolak epoxy acrylate                                                                           . . . 40%                                           Phenol novolak type epoxy resin                                                                         . . . 18%                                           Trimethylolpropane triacrylate                                                                          . . . 17%                                           Dipentaerythritol hexaacrylate                                                                          . . . 20%                                           Irgacure 184              . . . 3%                                            UVE1014 (manufactured by GE)                                                                            . . . 2%                                            Composition Example 6:                                                        o-cresol novolak epoxy acrylate                                                                         . . . 40%                                           Cresol novolak type epoxy resin                                                                         . . . 18%                                           Dipentaerythritol hexaacrylate                                                                          . . . 38%                                           Irgacure 184              . . . 2%                                            UVE1014 (manufactured by GE)                                                                            . . . 2%                                            Composition Example 7:                                                        Polyurethane acrylate     . . . 35%                                           Phenol novolak type epoxy resin                                                                         . . . 13%                                           Dipentaerythritol hexaacrylate                                                                          . . . 48%                                           UVE1014 (manufactured by GE)                                                                            . . . 2%                                            Irgacure 651              . . . 2%                                            Composition Example 8:                                                        Melamine acrylate         . . . 49%                                           Phenol novolak type epoxy resin                                                                         . . . 20%                                           Trimethylolpropane triacrylate                                                                          . . . 27%                                           UVE1014 (manufactured by GE)                                                                            . . . 2%                                            Irgacure 184              . . . 2%                                            Composition Example 9:                                                        Phenol novolak epoxy acrylate in which                                                                  . . . 60%                                           epoxy groups comprise about 30% of                                            acrylate groups                                                               Trimethylolpropane triacrylate                                                                          . . . 17%                                           Dipentaerythritol hexaacrylate                                                                          . . . 20%                                           Irgacure 184              . . . 3%                                            Composition Example 10:                                                       o-cresol novolak epoxy acrylate in which                                                                . . . 60%                                           epoxy groups comprise about 30% of                                            acrylate groups                                                               Dipentaerythritol hexaacrylate                                                                          . . . 38%                                           Irgacure 184              . . . 2%                                            Composition Example 11:                                                       Polyurethane acrylate in which                                                                          . . . 50%                                           epoxy groups comprise about 30% of                                            acrylate groups                                                               Dipentaerythritol hexaacrylate                                                                          . . . 48%                                           Irgacure 651              . . . 2%                                            Composition Example 12:                                                       Melamine acrylate in which                                                                              . . . 70%                                           epoxy groups comprise about 30% of                                            acrylate groups                                                               Trimethylolpropane triacrylate                                                                          . . . 27%                                           Irgacure 184              . . . 3%                                            ______________________________________                                    

Next, one example of the method of producing a protective film employinga photopolymerizable resin composition prepared as described above willbe explained with reference to the drawings.

As shown in FIG. 3(A), on a transparent substrate 31 having a coloredlayer 32 formed thereon, a photopolymerizable resin composition preparedas described above is first coated by a coater, e.g., a spin coater, aroll coater, a dip coater, a wheel coater, or a bar coater, so that thethickness of the dry film is on the order of 0.1 μm to 10 μm, preferably0.5 μm to 3 μm, thereby forming a photopolymerizable resin compositionlayer 33. After being dried, the photopolymerizable resin compositionlayer 33 is irradiated with ionizing radiation 35, e.g., ultravioletrays, by using a light source, e.g., a xenon lamp, a metal halide lamp,or an extra-high pressure mercury lamp, through a photomask 34 having apredetermined opening pattern, thereby effecting pattern exposure, asshown in FIG. 3(B). As a result of the pattern exposure, irradiatedportions are set. Then, the non-irradiated portions are selectivelyremoved by spray development or dip development with water or adeveloping solution comprising, for example, an organic solvent, asshown in FIG. 3(C).

FIG. 4(A) is a sectional view of a color filter formed with a coloredlayer for explanation of unevenness of a protective film. Colored pixelsR, G and B of a colored layer 41 are defined with a black matrix 42.There is a space 43 between each pair of adjacent colored pixels, andthere are differences 44 in level between the colored pixels R, G and B.If a protective film is formed over such a colored layer by using amaterial conventionally employed, relatively large irregularities areproduced in the surface of the protective film in accordance with theunderlying irregularities, so that the protective film is unfavorable interms of evenness, as shown in FIG. 4(B). However, in the case of theprotective film according to the present invention, even if there arelarge irregularities under the protective film, no large irregularitiesare produced in the surface thereof, so that the protective film isextremely excellent in evenness, as shown in FIG. 4(C). As a result, atransparent electrode film formed over the protective film is alsoexcellent in evenness.

It is possible to form a protective film only in a predetermined regionby exposing a photopolymerizable resin composition coating layer coatedover a colored layer through a photomask to thereby set it. As shown inFIG. 5(A), which is a sectional view of a color filter formed with aprotective film and a transparent electrode film, a step is formed atthe peripheral edge portion of a protective film 52 formed over atransparent substrate 51, so that a transparent electrode film 54 formedon the step portion 53 is smaller in thickness than that on the evenportion. Thus, there have heretofore been some problems. In particular,when the transparent electrode film is etched, it may be disconnected atthe thin portion. However, by effecting exposure in such a manner thatthe distance between the photomask and the photopolymerizable resincomposition is greater than the distance at which the image of thephotomask is properly drawn, it is possible to make the peripheral edgeportion 53 of the protective film gentle, as shown in FIG. 5(B).

Such exposure can be effected by using a proximity aligner shownschematically in FIG. 6. A proximity aligner 61 has a light source 62that emits ultraviolet light, for example, an extra-high pressuremercury lamp. Light from the light source 62 is formed into parallelrays by a parabolic mirror 63. Thereafter, the light path is changed bymirrors 64 and 65, and the light is applied to a photopolymerizableresin composition coating film formed on a substrate 68 placed on anexposure stage 67 through a photomask 66, thereby exposing the coatingfilm.

FIG. 7 shows the way in which exposure is effected by the apparatusshown in FIG. 6 in such a manner that the distance between the photomaskand the coating film is greater than the correct one. In this case,since the distance between a substrate 71 and a photomask 72 is greaterthan the proper distance for exposure, light passing through theperipheral portion 73 of the opening in the photomask 72 is dispersed,so that the peripheral edge portion 74 of the protective film has noclear distinction between the exposed and non-exposed portions. As aresult, the protective film has a gentle slope in thickness at theperipheral edge portion thereof.

Examples will be explained below.

EXAMPLE 1

A glass substrate (7059; manufactured by Corning Inc.) with a thicknessof 1.1 mm was employed as a substrate after being washed thoroughly, andcolored pixels were formed on the substrate. The formation of coloredpixels was carried out as follows:

(A) Formation of colored pixels:

A polyvinyl alcohol derivative in which a repeating unit represented bythe following formula was introduced in an amount of 1.2 mol % withrespect to the vinyl alcohol constitutional unit and which had anaverage polymerization degree of 1,700 and a saponification degree ofabout 88% was prepared: ##STR3##

Then, 10 parts by weight of Shimura Fast Pyrazolone Red BT (red pigment;manufactured by Dai-Nippon Ink & Chemicals, Inc.) were added to andmixed with 100 parts by weight of a 10% aqueous solution of the preparedpolyvinyl alcohol derivative. The resulting mixture was ground anddispersed in a ball mill, and the resulting dispersion was centrifugedat 10,000 rpm and filtered with a glass filter having a pore diameter of1 μm. The particle diameter distribution of the red photosensitive resincomposition thus obtained was analyzed by using a Coulter N4 submicronparticle analyzer (manufactured by Coulter). As a result, the averageparticle diameter was 0.17 μm, and particles having a particle diameterof 0.01 μm to 0.3 μm comprised 75% of all the particles. Next, the redphotosensitive resin composition was coated on the transparent glasssubstrate to a film thickness of 1.2 μm by using a spin coater and thendried for 30 minutes at 70° C. Thereafter, the coating film wassubjected to contact pattern exposure through a mosaic photomask. Then,the pattern-exposed photosensitive resin composition was spray-developedwith a developing solution comprising water and isopropyl alcohol in aweight ratio of 10:3, thereby selectively removing the non-exposedportions. Thereafter, heating was carried out for 30 minutes at 150° C.to form transparent red pixels.

Next, 10 parts by weight of Lyonol Green 2Y-301 (green pigment;manufactured by Toyo Ink Seizo K.K.) were added to and mixed with 100parts by weight of a 10% aqueous solution of the above-describedpolyvinyl alcohol derivative. The resulting mixture was ground anddispersed in a sand mill, and thereafter it was centrifuged at 12,000rpm and then filtered with a glass filter of 1.0 μm. The particlediameter distribution of the pigment in the obtained greenphotosensitive resin composition was analyzed in the same way as theabove. As a result, the average particle diameter was 0.13 μm, andparticles having a particle diameter of 0.01 μm to 0.3 μm comprised 91%of all the particles.

Next, the green photosensitive resin composition was spin-coated on thewhole surface of the glass substrate provided with the above-describedred transparent pixels to a film thickness of 1.2 μm and then dried for30 minutes at 70° C. Thereafter, the coating film was subjected topattern exposure through a mask having a predetermined configuration,thereby selectively removing the non-exposed portions, and then dryingwas carried out. Thus, transparent green pixels were formed in such amanner as to be adjacent to the above-described red transparent pixels.

Similarly, 3 parts by weight of Fast Gen Blue GNPS (blue pigment;manufactured by Dai-Nippon Ink & Chemicals, Inc.) were added to andmixed with 100 parts by weight of a 10% aqueous solution of theabove-described polyvinyl alcohol derivative. The resulting mixture wasground and dispersed in a sand mill, and the resulting dispersion wascentrifuged at 12,000 rpm and filtered with a glass filter having a porediameter of 1 μm. The particle diameter distribution of the pigment ofthe blue photosensitive resin composition thus obtained was analyzed inthe same way as the above. As a result, the average particle diameterwas 0.18 μm, and particles having a particle diameter of 0.01 μm to 0.3μm comprised 75% of all the particles. Next, the blue photosensitiveresin composition was spin-coated on the transparent glass substrateprovided with the above-described red and green transparent pixels to afilm thickness of 1.2 μm and then dried for 30 minutes at 70° C.Thereafter, the coating film was subjected to pattern exposure through amask having a predetermined configuration, thereby selectively removingthe non-exposed portions, and then drying was carried out. Thus,transparent blue pixels were formed in such a manner as to be adjacentto the green transparent pixels.

(B) Formation of a protective film:

Subsequently, 50 parts by weight of o-cresol novolak epoxy acrylate(molecular weight: 1,500 to 2,000) in which epoxy groups comprised about30% of the acrylate groups and 50 parts by weight of dipentaerythritolhexaacrylate (DPHA; manufactured by Nippon Kayaku Co., Ltd.) were mixedtogether as a photopolymerizable acrylate oligomer and a multifunctionalpolymerizable monomer, and further 2 parts by weight of Irgacure(manufactured by Ciba & Geigy Ltd.) was mixed as a photopolymerizationinitiator with the resulting mixture to prepare a blend, which was thendissolved in 200 parts by weight of ethyl Cellosolve acetate. Then, 10 gof the resulting solution was coated on the above-described coloredlayer to a thickness of 2.0 μm by using a spin coater. With a photomaskdisposed at a distance of 50 μm from the coating film, ultraviolet rayswere applied only to the coating film on the colored layer for 10seconds from an extra-high mercury lamp of 2.0 kW by using a proximityaligner. Subsequently, the coating film was dipped for 1 minute in adeveloping solution comprising 1,1,2,2-tetrachloroethane at atemperature of 25° C., thereby removing only the uncured portions of thecoating film.

Next, the protective film thus formed was coated with an ITO film to athickness of 0.4 μm by magnetron sputtering.

When the evenness of the transparent electrode layer was measured with aprobe type film thickness gauge, irregularities were as small as 0.01 μmto 0.05 μm. Thus, the transparent electrode layer had excellentevenness.

Even when the color filter thus obtained was heated to 250° C., noabnormality was found. Thus, it was confirmed that the color filter hadsatisfactory heat resistance. The light transmittance was alsoexcellent.

EXAMPLE 2

Ten parts by weight of the polyvinyl alcohol derivative shown in Example1 were dissolved in 100 parts by weight of water, and 5 parts by weightof Lyonol Green 2Y-301 (green pigment; manufactured by Toyo Ink SeizoK.K.) were added to and mixed with the resulting solution. The resultingmixture was ground and dispersed in a triple roll mill, and thereafterit was centrifuged at 6,000 rpm and then filtered with a glass filterhaving a pore diameter of 1 μm. Next, the green photosensitive resincomposition thus obtained was spin-coated over an 1 mm thick oftransparent glass substrate to a film thickness of 1.5 μm and then driedfor 30 minutes for 70° C. Thereafter, contact pattern exposure wascarried out through a mask. Then, the pattern-exposed photosensitiveresin composition was spray-developed with a developing solutioncomprising water and isopropyl alcohol in a weight ratio of 10:3,thereby selectively removing the unexposed portions. Thereafter, heatingwas carried out for 30 minutes at 150° C., thus forming green pixels.The transmittance of the green pixels in the region of 600 nm to 700 nmwas 1% or less, but the transmittance in the region of 500 nm to 560 nmwas 80% or more. The photo-sensitivity of the above-describedcomposition was 4 times that of the conventional gelatin/Cr coloredpixels. The edge configuration was substantially the same as that of thegelatin/Cr colored pixels. The particle diameter distribution of thepigment in the green transparent resin composition was analyzed by usinga Coulter N4 submicron particle analyzer. As a result, the averageparticle diameter was 0.08 μm, and particles having a particle diameterof 0.01 μm to 0.3 μm comprised 97% of all the particles.

EXAMPLE 3

After green pixels were formed in the same way as in Example 2 exceptthat the mixture of Lyonol Green 2Y-301 and the polyvinyl alcoholderivative was neither centrifuged nor filtered, the transmittance wasmeasured. As a result, the transmittance in the region of 500 nm to 560nm was 36.9%. Thus, it was revealed that the green pixels were unusableas colored pixels for a color filter.

EXAMPLE 4

Colored pixels were produced in the same way as in Example 1, and fourdifferent protective films were formed: a film formed from a resinmaterial having the same composition as that in Example 1 except thato-cresol novolak epoxy acrylate was used as an acrylate oligomer; a filmformed from the resin material used in Example 1; a film formed bycoating a 0.1% to 0.2% solution of γ-(2-aminoethyl)-aminopropyltrimethoxy silane (SH6020; manufactured by Toray Silicone K.K.), as asilane coupling agent, on a glass substrate, drying the coating film,and then coating the resin material used in Example 1; and a film formedfrom the resin material used in Example 1 which had a silane couplingagent added thereto. Then, the bond strength of each of the coatingfilms was evaluated by the cross-cut adhesion test (JIS K5400). Resultsof the test are shown in Table 1 below. The cross-cut adhesion test wascarried out for each coating film after the completion of the process inwhich a film material was coated on a transparent substrate (7059;manufactured by Corning Inc.) to a thickness of 1.0 μm to 1.5 μm anddried, and the coating film was exposed for 10 seconds by using anextra-high pressure mercury lamp of 2.0 kW so as to be cured and thendipped in boiling water for 60 minutes together with the substrate.

The protective film according to the present invention and theprotective films treated with a silane coupling agent had excellentcharacteristics in terms of the bond strength and showed no change inthe characteristics in terms of the transparency and the lighttransmission properties.

                  TABLE 1                                                         ______________________________________                                        Processing method                                                                             Evaluation grades                                                                          Conditions                                       ______________________________________                                        Epoxy acrylate alone                                                                           0           not less than                                                                 65% separated                                    Epoxy group-containing                                                                         8           not more than                                    epoxy acrylate               5% separated                                     Epoxy group-containing                                                                        10           No separation                                    epoxy acrylate, and                                                           treatment of substrate                                                        with coupling agent                                                           Epoxy group-containing                                                                        10           No separation                                    epoxy acrylate having                                                         coupling agent added thereto                                                  ______________________________________                                    

EXAMPLE 5

Colored pixels were produced in the same way as in Example 1, and aprotective film was formed as follows: 50 parts by weight of o-cresolnovolak epoxy acrylate (molecular weight: 1,500 to 2,000), as aphotopolymerizable acrylate oligomer, and 50 parts by weight ofdipentaerythritol hexaacrylate (DPHA; manufactured by Nippon Kayaku Co.,Ltd.), as a multifunctional polymerizable monomer, were mixed together,and 2 parts by weight of Irgacure (manufactured by Ciba & Geigy Ltd.)were mixed with the resulting mixture to form a blend, which was thendissolved in 200 parts by weight of ethyl Cellosolve acetate. Then, 10 gof the resulting solution was coated on the above-described coloredlayer to a thickness of 2.0 μm by using a spin coater. With a photomaskdisposed, ultraviolet rays were applied only to the coating film on thecolored layer for 10 seconds from an extra-high mercury lamp of 2.0 kWby using a proximity aligner. Subsequently, the coating film was dippedfor 1 minute in a developing solution comprising1,1,2,2-tetrachloroethane at a temperature of 25° C., thereby removingonly the uncured portions of the coating film.

Next, the protective film thus formed was coated with an ITO film to athickness of 0.4 μm by magnetron sputtering.

When the evenness of the transparent electrode layer was measured with aprobe type film thickness gauge, irregularities were as small as 0.01 μmto 0.05 μm. Thus, the transparent electrode layer had excellentevenness.

Even when the color filter thus obtained was heated to 250° C., noabnormality was found. Thus, it was confirmed that the color filter hadsatisfactory heat resistance.

EXAMPLE 6

The bond strength of each of the following coating films was evaluatedby the cross-cut adhesion test (JIS K5400): a film formed by coating a0.1% to 0.2% solution of γ-(2-aminoethyl)-aminopropyl trimethoxy silane(SH6020; manufactured by Toray Silicone K.K.), as a silane couplingagent, on a glass substrate, and then coating a resin composition havingthe same composition as that of the resin composition used in Example 5;and a film formed from the resin composition used in Example 5 which hada silane coupling agent added thereto. Results of the test are shown inTable 2 below. In Table 2, "Treatment of substrate" means the treatmentof the substrate with a silane coupling agent, and "Addition to resin"means the addition of a silane coupling agent to the resin material usedin Example 5.

The protective film according to the present invention and theprotective film treated with a silane coupling agent had excellentcharacteristics in terms of the bond strength and showed no change inthe characteristics in terms of the transparency and the lighttransmission properties.

                  TABLE 2                                                         ______________________________________                                        Processing method                                                                            Evaluation grades                                                                          Conditions                                        ______________________________________                                        Resin used in Example 5                                                                       0           not less than                                                                 65% separated                                     Treatment of substrate                                                                       10           No separation                                     Addition to resin                                                                            10           No separation                                     ______________________________________                                    

EXAMPLE 7

A color filter was produced in the same way as in Example 1 except thatthe following material was used as a photopolymerizable protective filmcomposition.

As a photopolymerizable acrylate oligomer, 35 parts by weight ofo-cresol novolak epoxy acrylate (molecular weight: 1,500 to 2,000) and15 parts by weight of a cresol novolak type epoxy resin, and as amultifunctional polymerizable monomer, 50 parts by weight ofdipentaerythritol hexaacrylate (DPHA; manufactured by Nippon Kayaku Co.,Ltd.) were mixed together, and the resulting mixture was further mixedwith 2 parts by weight of Irgacure (manufactured by Ciba & Geigy Ltd.),as a polymerization initiator, and 2 parts by weight of UVE1014(manufactured by General Electric Co.), as an epoxy curing agent. Theresulting blend was dissolved in 200 parts by weight of ethyl Cellosolveacetate. Then, 10 g of the resulting solution was coated on theabove-described colored layer to a thickness of 2.0 μm by using a spincoater. With a photomask disposed at a distance of 100 μm from thecoating film, ultraviolet rays were applied only to the surface of thecolored layer for 10 seconds from an extra-high mercury lamp of 2.0 kWby using a proximity aligner. Subsequently, the coating film was dippedfor 1 minute in a developing solution comprising1,1,2,2-tetrachloroethane at a temperature of 25° C., thereby removingonly the uncured portions of the coating film.

The hardness of the resulting protective film was equivalent to 7H interms of the pencil hardness.

Next, the protective film thus formed was coated with an ITO film to athickness of 0.4 μm by magnetron sputtering.

When the evenness of the transparent electrode layer was measured with aprobe type film thickness gauge, irregularities were as small as 0.01 μmto 0.05 μm. Thus, the transparent electrode layer had excellentevenness.

Even when the color filter thus obtained was heated for 1 hour at 250°C., no abnormality was found. Thus, it was confirmed that the colorfilter had satisfactory heat resistance.

EXAMPLE 8

Color filters were produced in the same way as in Example 7 except thatthe following photopolymerizable compositions were used.

(a) A film formed from a resin material obtained by mixing together 50parts by weight of o-cresol novolak epoxy acrylate (molecular weight:1,500 to 2,000) and 50 parts by weight of dipentaerythritol hexaacrylate(DPHA; manufactured by Nippon Kayaku Co., Ltd.) and further mixing theresulting mixture with 2 parts by weight of Irgacure (manufactured byCiba & Geigy Ltd.), as a polymerization initiator.

(b) A film formed from the resin material used in Example 7.

(c) A film formed by coating a 0.1% solution ofγ-(2-aminoethyl)-aminopropyl trimethoxy silane (SH6020; manufactured byToray Silicone K.K.), as a silane coupling agent, on a glass substrate,drying the coating film, and then coating the resin material used inExample 7.

(d) A film formed from the resin material used in Example 7 which had asilane coupling agent added thereto.

Then, the bond strength of each of the coating films was evaluated bythe cross-cut adhesion test (JIS K5400). Results of the test are shownin Table 3 below. The cross-cut adhesion test was carried out for eachcoating film after the completion of the process in which a filmmaterial was coated on a transparent substrate (7059; manufactured byCorning Inc.) to a thickness of 1.0 μm to 1.5 μm and dried, and thecoating film was exposed for 10 seconds by using an extra-high pressuremercury lamp of 2.0 kW so as to be cured and then dipped in boilingwater for 60 minutes together with the substrate.

                  TABLE 3                                                         ______________________________________                                        Processing method                                                                             Evaluation grades                                                                          Conditions                                       ______________________________________                                        (a) Epoxy acrylate alone                                                                       0           not less than                                                                 65% separated                                    (b) Epoxy resin-containing                                                                     8           not more than                                    epoxy acrylate               5% separated                                     (c) Epoxy resin-containing                                                                    10           No separation                                    epoxy acrylate, and                                                           treatment of substrate                                                        with coupling agent                                                           (d) Epoxy resin-containing                                                                    10           No separation                                    epoxy acrylate having                                                         coupling agent added thereto                                                  ______________________________________                                    

EXAMPLE 9

In the same way as in Example 7, as a photopolymerizable acrylateoligomer, 50 parts by weight of o-cresol novolak epoxy acrylate(molecular weight: 1,500 to 2,000) and, as a multifunctionalpolymerizable monomer, 50 parts by weight of dipentaerythritolhexaacrylate (DPHA; manufactured by Nippon Kayaku Co., Ltd.) were mixedtogether, and the resulting mixture was further mixed with 2 parts byweight of Irgacure (manufactured by Ciba & Geigy Ltd.), as apolymerization initiator. The resulting blend was dissolved in 200 partsby weight of ethyl Cellosolve acetate. Then, 10 g of the resultingsolution was coated on the colored layer to a thickness of 2.0 μm byusing a spin coater.

Subsequently, with a photomask disposed at a distance of 500 μm,exposure was carried out by using the proximity aligner shown in FIG. 6.

The exposure was effected in such a manner that ultraviolet rays wereapplied only to the coating film on the colored layer for 10 seconds byusing an extra-high pressure mercury lamp of 2.0 kW. Subsequently, thecoating film was dipped for 1 minute in a developing solution comprising1,1,2,2-tetrachloroethane at a temperature of 25° C., thereby removingonly the uncured portions of the coating film.

The section of the peripheral edge portion of the resulting protectivefilm had a gentle slope at about 10 degrees to the substrate.

Next, the protective film thus formed was coated with an ITO film to athickness of 0.4 μm by magnetron sputtering.

Then, the ITO film was etched with an etching solution comprising ferricchloride and hydrochloric acid, thereby obtaining a color filter formedwith the ITO patterns having a line width of 100 μm and a spacing of 20μm. The transparent electrode layer had a sufficiently high bondstrength at the peripheral edge portion, so that no disconnectionoccurred.

EXAMPLE 10

A protective film was formed in the same way as in Example 7 except thatthe distance between the photomask and the coating film was 300 μm. Thesection of the peripheral edge portion of the resulting protective filmhad a gentle slope at about 15 degrees to the substrate.

Next, the protective film thus formed was coated with an ITO film to athickness of 0.4 μm by magnetron sputtering.

Then, the ITO film was etched with an etching solution comprising ferricchloride and hydrochloric acid, thereby obtaining a color filter formedwith the ITO patterns having a line width of 100 μm and a spacing of 20μm. The transparent electrode layer had a sufficiently high bondstrength at the peripheral edge portion, so that no disconnectionoccurred.

EXAMPLE 11

A protective film was formed in the same way as in Example 1 except thatno multifunctional photopolymerizable monomer was added.

The hardness of the resulting protective film was equivalent to HB to 2Hin terms of the pencil hardness.

Subsequently, the protective film was coated with an ITO film in thesame way as in the example. Wrinkles were developed in the ITO filmhaving a thickness of 0.15 μm. Irregularities were 0.1 μm to 0.5 μm, andthe heat resistance was 220° C.

EXAMPLE 12

A protective film was formed in the same way as in Example 1 except thata thermosetting acrylate (trademark JSS181, manufactured by JapanSynthetic Rubber Co., Ltd.) was employed as a protective film materialand the curing of the protective film was effected by heating for 1 hourat 180° C.

The hardness of the resulting protective film was equivalent to HB to 4Hin terms of the pencil hardness.

Subsequently, the protective film was coated with an ITO film in thesame way as in the example. Wrinkles were developed in the ITO filmhaving a thickness of 0.1 μm. Irregularities were 0.2 μm to 0.7 μm, andthe heat resistance was 200° C.

EXAMPLE 13

A protective film was formed in the same way as in the example exceptthat a thermosetting epoxy resin (trademark CZ-003, manufactured byNissan Chemicals Industries Ltd.) was employed as a protective filmmaterial and the curing of the protective film was effected by heatingfor 1 hour at 180° C.

The hardness of the resulting protective film was equivalent to HB to 2Hin terms of the pencil hardness.

Subsequently, the protective film was coated with an ITO film in thesame way as in the example. Wrinkles were deveIoped in the ITO filmhaving a thickness of 0.1 μm. Irregularities were 0.2 μm to 0.7 μm, andthe heat resistance was not higher than 200° C.

EXAMPLE 14

A protective film was formed in the same way as in the example exceptthat a silicone resin (trademark TDA1H, manufactured by Shokubai KaseiK.K.) was employed as a protective film material and the curing of theprotective film was effected by heating for 1 hour at 180° C.

The hardness of the resulting protective film was equivalent to 3H to 9Hin terms of the pencil hardness, and the heat resistance was excellent,i.e., not lower than 250° C. However, when the protective film wascoated with an ITO film in the same way as in the example, there werecracks in the ITO film having a thickness of not less than 0.2 μm.Irregularities were 0.2 μm to 0.7 μm.

EXAMPLE 15

A color filter was produced in the same way as in Example 7 except thatthe distance between the photomask and the coating film was 100 μm. Thesection of the peripheral edge portion of the resulting protective filmhad a slope at about 23 degrees to the substrate. Next, an ITO film wasformed over the protective film in the same way as in Example 1 and thenetched to thereby obtain a color filter formed with the ITO patternshaving a line width of 100 μm and a spacing of 20 μm.

The transparent electrode layer had a low bond strength at theperipheral edge portion, so that disconnection occurred.

EXAMPLE 16

A color filter was produced in the same way as in Example 7 except thatthe distance between the photomask and the coating film was 50 μm. Thesection of the peripheral edge portion of the resulting protective filmhad a slope at about 31 degrees to the substrate. Next, an ITO film wasformed over the protective film in the same way as in Example 1 and thenetched to thereby obtain a color filter formed with the ITO patternshaving a line width of 100 μm and a spacing of 20 μm.

The transparent electrode layer had a low bond strength at theperipheral edge portion, so that disconnection occurred.

EXAMPLE 17

A color filter was produced in the same way as in Example 7 except thatthe distance between the photomask and the coating film was 30 μm. Thesection of the peripheral edge portion of the resulting protective filmhad a slope at about 36 degrees to the substrate. Next, an ITO film wasformed over the protective film in the same way as in Example 1 and thenetched to thereby obtain a color filter formed with the ITO patternshaving a line width of 100 μm and a spacing of 20 μm.

The transparent electrode layer had a low bond strength at theperipheral edge portion, so that disconnection occurred.

As shown in FIG. 8, in which the distance between the photomask and thecoating film is plotted along the abscissa axis and the angle ofinclination of the peripheral edge portion of the protective film isplotted along the ordinate axis, the inclination angle can be reduced bysetting the distance between the photomask and the photopolymerizableresin composition coating film to be greater than the correct distance.

INDUSTRIAL APPLICABILITY

The color filter according to the present invention and a liquid crystaldisplay using it use a transparent resin material to form a coloredlayer, the material having a pigment dispersed therein which has such aparticle diameter distribution that particles having a particle diameterof 1 μm or more comprise not more than 5% of all the pigment particlesby weight. Accordingly, the light transmittance in the light absorbingregion on the spectral characteristic curve in the visible region is notmore than 20%, while the light transmittance in the light transmittingregion is not less than 50%. In addition, since the colored layer issuperior in both heat resistance and light resistance, it is notdeteriorated during the heat treatment in the process of producing thecolor filter. Further, the protective film that is formed over thecolored layer has sufficiently high heat resistance and hardness, andthe peripheral edge portion of the protective film is gentle, so that atransparent electrode film of excellent characteristics can be formedover the protective film. Thus, it is possible to provide a color filterand a color liquid crystal display, which provide superior displayquality.

What is claimed is:
 1. A method of producing a color filter having aprotective film formed over colored pixels formed on a transparentsubstrate by curing a photopolymerizable resin composition, comprisingthe steps of: irradiating only a predetermined region of aphotopolymerizable resin composition coating film with light to curesaid region; and dissolvingly removing the uncured portion of thephotopolymerizable resin composition by using a solution which iscompatible with the photopolymerizable resin composition in the uncuredregion, thereby forming a protective film only in a predeterminedregion, wherein said irradiation with light is effected through aphotomask that is disposed at a distance which is greater than thecorrect distance between the photomask and the coating film, therebydispersing light passing through the peripheral portion of the openingin the photomask so as to change the film thickness of the peripheraledge portion of the protective film.
 2. A color filter according toclaim 1, wherein said colored pixels are formed from a transparent resinmaterial having a pigment dispersed therein.
 3. A color filtercomprising a transparent substrate, colored pixels formed on saidsubstrate, and a protective film formed over said pixels, wherein saidprotective film comprises a cured photopolymerizable resin compositionwhich contains at least a photopolymerizable acrylate oligomer and amultifunctional photopolymerizable acrylate monomer having at least twofunctional groups in one molecule, and wherein said photopolymerizableresin composition is coated on a silane coupling agent film, which is onsaid transparent substrate.
 4. A color filter comprising a transparentsubstrate, colored pixels formed on said substrate, and a protectivefilm formed over said pixels, wherein said protective film comprises acured photopolymerizable resin composition which contains at least aphotopolymerizable acrylate oligomer and dipentaerythritol hexaacrylateand wherein said photopolymerizable resin composition is coated with asilane coupling agent added thereto.
 5. A color filter according toclaim 4, wherein the thickness of the peripheral edge portion of saidprotective film varies gently.
 6. A color filter according to claim 4,wherein said colored pixels are formed from a transparent resin materialhaving a pigment dispersed therein.
 7. A color filter comprising atransparent substrate, colored pixels formed on said substrate, and aprotective film formed over said pixels, wherein said protective filmcomprises a cured photopolymerizable resin composition which contains atleast a photopolymerizable acrylate oligomer and dipentaerythritolhexaacrylate and wherein the thickness of the peripheral edge portion ofsaid protective film varies gently.
 8. A color filter according to claim7, wherein said colored pixels are formed from a transparent resinmaterial having a pigment dispersed therein.
 9. A color filtercomprising a transparent substrate, colored pixels formed on saidsubstrate, and a protective film formed over said pixels, wherein saidprotective film comprising a cured photopolymerizable resin compositionwhich contains at least a photopolymerizable acrylate oligomer anddipentaerythritol hexaacrylate, wherein said colored pixels are formedfrom a transparent resin material having a pigment dispersed therein.10. A method of producing a color filter having a protective film formedover colored pixels formed on a transparent substrate by curing aphotopolymerizable resin composition, comprising the steps of:irradiating only a predetermined region of a photopolymerizable resincomposition coating film with light to cure said region; anddissolvingly removing the uncured portion of the photopolymerizableresin composition by using a solution which is compatible with thephotopolymerizable resin composition in the uncured region, therebyforming a protective film only in a predetermined region, wherein saidphotopolymerizable resin composition is coated on a silane couplingagent film, which is on said transparent substsrate.
 11. A method ofproducing a color filter having a protective film formed over coloredpixels formed on a transparent substrate by curing a photopolymerizableresin composition, comprising the steps of: irradiating only apredetermined region of a photopolymerizable resin composition coatingfilm with light to cure said region; and dissolvingly removing theuncured portion of the photopolymerizable resin composition by using asolution which is compatible with the photopolymerizable resincomposition in the uncured region, thereby forming a protective filmonly in a predetermined region, wherein said photopolymerizable resincomposition is coated with silane coupling agent added thereto.